Prenatal Development 2024 PDF

CHAPTER 3 OVERVIEW OF PRENATAL DEVELOPMENT TO ACCOMPANY ILLUSTRATED DENTAL EMBRYOLOGY, HISTOLOGY, AND ANATOMY, 5TH EDITION  LEARNING OBJECTIVES Define and Define and pronounce the key terms in this pronounc chapter. e Outline the periods of prenatal Outline...

CHAPTER 3 OVERVIEW OF PRENATAL DEVELOPMENT TO ACCOMPANY ILLUSTRATED DENTAL EMBRYOLOGY, HISTOLOGY, AND ANATOMY, 5TH EDITION  LEARNING OBJECTIVES Define and Define and pronounce the key terms in this pronounc chapter. e Outline the periods of prenatal Outline development, describing the major events that occur during the early weeks. Integrate a background on prenatal Integrate development into the development of the face, neck, and oral structures. PRENATAL DEVELOPMENT OVERVIEW OF EMBRYOLOGY PERIODS OF PRENATAL DEVELOPMENT Table 3.1  EMBRYOLOGY STUDY OF PRENATAL DEVELOPMENT DEVELOPMENT > FACE AND ORAL CAVITY THE PREIMPLANTATION PERIOD AND THE EMBRYONIC PERIOD MAKE UP THE FIRST TRIMESTER OF THE PREGNANCY, AND THE FETAL PERIOD CONSTITUTES THE LAST TWO TRIMESTERS.  SPERM + OVUM EMBRYON > FERTILIZED EGG (ZYGOTE) IC – DIVIDES GEOMETRICALLY STAGES 2 > 4 > 8 > 16 …..  PREIMPLANTATION PERIOD AFTER FERTILIZATION, THE ZYGOTE UNDERGOES MITOSIS (CELL DIVISION OR CLEAVAGE). THE ZYGOTE BECOMES A VESICLE KNOWN AS A BLASTOCYST (OR BLASTULA) BECAUSE OF THE ONGOING PROCESS OF MITOSIS Figure 3.3  ZYGOTE (PREIMPLANTATION PERIOD) > FERTILIZED EGG -- 1 WEEK EMBRYO (EMBRYONIC PERIOD) STAGES > 2 -- 8 WEEKS FETUS (FETAL PERIOD) > 9 -- 38 TO 42 WEEKS (END OF PREGNANCY)  THE IMPLANTED BLASTOCYST GROWS BY INCREASED PROLIFERATION OF THE EMBRYONIC CELLS, WITH DIFFERENTIATION ALSO OCCURRING, RESULTING IN CHANGES IN CELLULAR MORPHOGENESIS; EVERY RIDGE, BUMP, SECOND AND RECESS NOW INDICATE THESE INCREASED LEVELS OF CELLULAR WEEK DIFFERENTIATION. THIS INCREASED NUMBER OF EMBRYONIC CELLS CREATES THE EMBRYONIC CELL LAYERS (OR GERM LAYERS) WITHIN THE BLASTOCYST.  THIRD WEEK DURING THE BEGINNING OF THE THIRD WEEK OF PRENATAL DEVELOPMENT, WITHIN THE EMBRYONIC PERIOD, THE PRIMITIVE STREAK FORMS WITHIN THE BILAMINAR EMBRYONIC DISC. Bilaminar embryonic disc Figure 3.7  THIRD WEEK THIS FURROWED, ROD‑SHAPED THICKENING IN THE MIDDLE OF THE DISC RESULTS FROM AN INCREASED PROLIFERATION OF CELLS IN THE MIDLINE AREA. THE PRIMITIVE STREAK CAUSES THE DISC TO HAVE BILATERAL SYMMETRY, WITH A RIGHT HALF AND LEFT HALF. Figure 3.7  THE BEGINNING OF THE THIRD WEEK, SOME CELLS FROM THE EPIBLAST LAYER MOVE OR MIGRATE TOWARD THE HYPOBLAST LAYER ONLY IN THE AREA OF THE PRIMITIVE STREAK. THIRD WEEK THESE MIGRATORY CELLS LOCATE IN THE MIDDLE, BETWEEN THE EPIBLAST AND HYPOBLAST LAYERS, AND BECOME MESENCHYME (AN EMBRYONIC CONNECTIVE TISSUE). Figure 3.8  THIRD WEEK THE TRILAMINAR DISC HAS THREE EMBRYONIC CELL LAYERS, OR GERM LAYERS. WITH THE CREATION OF THIS NEW EMBRYONIC CELL LAYER OF MESODERM, THE EPIBLAST LAYER IS NOW CONSIDERED Figure 3.9  THIRD WEEK THE DISC NOW HAS A CEPHALIC END, OR HEAD END. AT THE CEPHALIC END, THE OROPHARYNGEAL MEMBRANE (OR BUCCOPHARYNGEAL MEMBRANE) FORMS, CONSISTING OF ONLY ECTODERM EXTERNALLY AND ENDODERM INTERNALLY WITHOUT ANY INTERMEDIATE MESODERM. Figure 3.9  CEPHALIC END MORE ADVANCED IN DEVELOPMENT THAN CAUDAL END END OF 3RD WEEK - BEGINNING OF 4TH PREFACIAL WEEK EMBRYOLO GY > FACIAL FEATURES > STOMODEUM (PRIMITIVE MOUTH) ESTABLISHED  MASS OF TUBULAR CELLS MOUTH END > CEPHALIC (HEAD) ANAL END ZYGOTE > CAUDAL (TAIL) TUBE WITHIN A TUBE > CLOSED AT BOTH ENDS  THREE LAYERS ECTODERM PRIMARY > ECTO : OUTSIDE EMBRYO MESODERM NIC > MESO : MIDDLE LAYERS ENDODERM > ENDO : INSIDE  EPITHELIAL COVERING OUTSIDE OF BODY (EPIDERMIS) EPITHELIAL LININGS > ORAL CAVITY ECTODE > NASAL CAVITY RM > SINUSES > ENAMEL > NERVOUS SYSTEM  DERMIS BONE (SKELETAL SYSTEM) MUSCLE MESODE BLOOD CELLS RM LYMPHATICS KIDNEYS DENTIN, PULP, CEMENTUM, PDL REPRODUCTIVE ORGANS  EPITHELIAL LININGS OF GI & RESPIRATORY TRACT AND ASSOCIATED ORGANS > PHARYNX ENDODE > STOMACH RM > INTESTINES > LIVER > LUNGS  INCREASE IN WEIGHT AND SIZE REQUIRES INCREASE IN GROWT > NUMBER OF CELLS H > SIZE OF CELLS > PRODUCT OF CELLS  3 WEEKS – 3 MM 8 WEEKS – 23 MM FETUS 3 MONTHS – 61 MM SIZE 4 MONTHS – 116 MM  CEPHALIC END (ECTODERM) INVAGINATES INTO A DEPRESSION AND CONTACTS ENDODERM OF FOREGUT STOMODEU M OROPHARYNGEAL (BUCCOPHARYNGEAL) MEMBRANE SEPARATES STOMODEUM FROM FORGUT LOCATION: AREA OF PALATINE TONSIL  STOMODEUM > ECTODERM FOREGUT LININGS > ENDODERM NO MESODERM BETWEEN  END OF 3RD WEEK > INVAGINATION IN ROOF, ANTERIOR TO OROPHARYNGEAL (BUCCOPHARYNGEAL) MEMBRANE RATHKE PIT ’S CONTINUES TOWARD BRAIN POUCH FORMS > ANTERIOR LOBE OF HYPOPHYSIS (PITUITARY GLAND)  THE DISC UNDERGOES EMBRYONIC FOLDING, ESTABLISHING FOR THE FIRST TIME THE AXIS, WHICH PLACES FOURTH FORMING TISSUE TYPES INTO WEEK THEIR PROPER POSITIONS FOR FURTHER EMBRYONIC DEVELOPMENT AS WELL PRODUCING A SOMEWHAT- TUBULAR EMBRYO.  BUCCOPHARYNGEAL MEMBRANE RUPTURES FOURTH COMMUNICATION ESTABLISHED WEEK BETWEEN THE STOMODEUM AND PRIMITIVE DIGESTIVE TRACT  CLINICAL CONSIDERATIONS FOR PREIMPLANTATION PERIOD If any disturbances occur in the basic process of meiosis during fertilization, then major congenital malformations 1 out of 10 cases Examples: Ectopic pregnancy and Down syndrome (trisomy 21) Signs & Symptoms of Down syndrome: Orofacial features: flat broad face with widely spaced eyes, flat bridged nose, oblique eyelid fissures, furrowed lower lip, tongue fissures, lingual papillae hypertrophy and various intellectual disability May include delayed tooth eruption, fewer teeth w/ microdontia and increased level of perio. disease Arched palate and weak tongue muscles leading to an open mouth w/ tongue protrusion and speech difficulties  DOWN SYNDROME (TRISOMY 21) Figure  CLINICAL CONSIDERATIONS FOR THE EMBRYONIC PERIOD Beginning of essential external & internal structure formation Most critical period of prenatal development Examples: Ectodermal dysplasia (abnormalities of teeth, skin, hair, nails, eyes, facial structure and glands) – partial or complete anodontia – frequently have developmental disturbances Treacher Collins Syndrome – downward slanting eyes, underdeveloped zygomatic bone, drooping lateral lower eyelids, hearing loss with malformed or absent ears and anadontia, enamel dysplasia and micrognathia Teratogenic effects – Rubella (cataracts, cardiac defects, deafness), Syphilis (Treponema Pallidum) – Hutchinson incisor, Mullberry molars, blindness, deafness and maybe paralysis Fetal Alcohol syndrome – high levels of ethanol ingested – growth deficiency, intellectual disability, small head circumference, low nasal bridge, short nose, small midface, widely spaced eyes w/ epicanthic folds, eyelid fissures, indistinct philtrum and thin upper lip – No safe time or amount of alcohol known Radiation – severity of damage related to dose, dose rate and state of development at exposure Spina bifida – Neural tube defect (spinal cord)  ECTODERMAL DYSPLASIA http://4.bp.blogspot.com/_9JAvD1q-aU8/TLicP-y4cQI/AAAAAAAAAK0/n07sRAQuXC8/s1600/  TREACHER COLLINS SYNDROME Figure 3.16 HUTCHINSON INCISORS & MULBERRY MOLAR Figure 3.17A Figure 3.17B  FETAL ALCOHOL SYNDROME Figure 3.18  CLINICAL CONSIDERATIONS FOR FETAL PERIOD Tetracycline stain – Tetracycline antibiotic therapy of pregnant women Children’s primary teeth developing at the time appear yellow-brown discoloration in varying degrees Permanent teeth may also be affected if drug is given to a child during their development Treatment may require crowns, veneers or extensive vital tooth whitening Overuse of amoxicillin in children with ear/respiratory infections may be involved in pitting & intrinsic stain in permanent teeth enamel (enamel dysplasia)  TETRACYCLINE STAIN Figure 3.19 https://www.clarencetam.co.nz/wp- content/uploads/2020/06/CPT6481.jpg CHAPTER 4: DEVELOPMENT OF THE FACE AND NECK TO ACCOMPANY ILLUSTRATED DENTAL EMBRYOLOGY, HISTOLOGY, AND ANATOMY, 5TH EDITION  LEARNING OBJECTIVES Define Define and pronounce the key terms in this and chapter. pronounce Outline the events that occur during the Outline development of the face and neck, describing each step in their formation. Integrate the knowledge of the development of the face and neck into understanding the Integrate observed structures and any developmental disturbances of these structures. OVERVIEW OF FACIAL DEVELOPMENT DEVELOPMENT OF THE FACE  THE FACE AND ITS ASSOCIATED TISSUE BEGIN TO FORM DURING THE FOURTH WEEK OF PRENATAL DEVELOPMENT OVERVIEW (EMBRYONIC PERIOD). OF FACIAL DEVELOPM DURING THIS TIME, THE RAPIDLY ENT GROWING BRAIN OF THE EMBRYO BULGES OVER THE OROPHARYNGEAL MEMBRANE AND DEVELOPING HEART.  FOURTH WEEK FINALLY, DURING THE FOURTH WEEK, THE FACE AND NECK BEGIN TO DEVELOP, WITH THE PRIMITIVE EYES, EARS, NOSE, ORAL CAVITY, AND JAW AREAS. Figure 4.1  DEVELOPS FROM TWO EMBRYONIC EARLY STRUCTURES FACIAL DEVELOPME > FRONTONASAL (FRONTAL) PROCESS NT > 1ST BRANCHIAL ARCH  BULGE ABOVE STOMODEUM FRONTONA > UPPER FACE SAL > NASAL SEPTUM (FRONTAL) PROCESS > ANTERIOR HARD PALATE  BELOW STOMODEUM SIX PAIRED (I, II, III, IV, V, VI) > I: MANDIBLE, PART OF MAXILLA BRANCHI > I, II, III, IV: TONGUE AL FRONTONASAL (FRONTAL) ARCHES PROCESS AND 1ST BRANCHIAL ARCH > FACE, ORAL AND NASAL CAVITIES Figure 4.11 (3rd Edition)  MAXILLARY PROCESSES (2) > ROUNDED PROCESS ON EACH SIDE 1 ST BRANCHI > GROWS UPWARD AND AL ARCH MEDIALLY MANDIBULAR PROCESSES (2) > REMAINDER OF 1ST ARCH  SIDES OF MAXILLA MAXILLA SIDES OF UPPER LIP RY MOST OF PALATE PROCES UPPER CHEEKS (ABOVE LINEA S ALBA)  LOWER CHEEK (BELOW LINEA ALBA) MANDIBU LOWER LIP LAR PROCESS MANDIBLE MAJORITY OF TONGUE  SMALL DEPRESSIONS ON THE FRONTAL PROCESS > LOCATION: LOWER BORDER OLFACTO DIVIDES LOWER FRONTAL INTO 3 PARTS RY > MEDIAL NASAL PROCESS (NASAL) (CENTER) PITS > LATERAL NASAL PROCESSES (2) (RIGHT AND LEFT)  CENTER AND TIP OF NOSE MEDIAL NASAL NASAL SEPTUM PROCES GLOBULAR PROCESS S (INTERMAXILLARY SEGMENT) LATERAL NASAL SIDES OF NOSE (RIGHT AND LEFT) PROCES SES  FORMS FROM LOWER BORDER OF MEDIAL NASAL PROCESS GLOBULAR EXTENDS BETWEEN RIGHT AND PROCESS LEFT MAXILLARY PROCESSES (INTERMAXIL LARY FORMS SEGMENT) PHILTRUM PREMAXILLA  STRUCTURES CHANGE POSITION > EYES AND EARS MOVE INTO POSITION FUSE WITH GLOBULAR PROCESS (INTERMAXILLARY SEGMENT) MAXILLA RY > GLOBULAR FORMS - CENTER OF UPPER LIP PROCESS (PHILTRUM) ES MAXILLARY PROCESSES FORM > SIDES OF UPPER LIP LIP COMPLETE: END OF 2ND MONTH  DISINTEGRATION OF THE OROPHARYNGEAL MEMBRANE ENLARGES THE STOMODEUM OF THE EMBRYO AND ALLOWS ACCESS BETWEEN THE PRIMITIVE MOUTH AND THE PRIMITIVE PHARYNX. THE MANDIBULAR PROCESSES ALSO FUSE, FORMING THE MANDIBULAR ARCH INFERIOR TO THE ENLARGED STOMODEUM. FIGURE 4.5 Figure 4.3  RIGHT AND LEFT MAXILLARY PROCESS AND MANDIBULAR MORE PROCESS FUSION DECREASES WIDTH OF MOUTH  EXTREMELY LARGE MOUTH FAILURE OF COMPLETE FUSION MACROSTOMI A OF MAXILLARY PROCESSES AND MANDIBULAR PROCESSES  DETERMINED AT TIME OF FUSION OF MAXILLARY AND MANDIBULAR FORDYC PROCESSES E SPOTS SEBUM FROM MISPLACED OR TRAPPED SEBACEOUS GLAND TISSUE IS ENTRAPPED CHAPTER 5: DEVELOPMENT OF OROFACIAL STRUCTURES TO ACCOMPANY ILLUSTRATED DENTAL EMBRYOLOGY, HISTOLOGY, AND ANATOMY, 5TH EDITION  LEARNING OBJECTIVES Define and Define and pronounce the key terms in this pronounc chapter. e Outline the events that occur during the Outline development of the orofacial structures, describing each step of formation. Integrate the knowledge of the development of the orofacial structures into Integrate understanding the present structure of the tissues and any developmental disturbances involved in these structures.  THE OROFACIAL STRUCTURES DISCUSSED IN THIS CHAPTER DEVELOP DURING THE FOURTH WEEK TO THE TWELFTH WEEK OF PRENATAL DEVELOPMENT, (THE LATER EMBRYONIC OROFACIAL PERIOD AND EARLY FETAL PERIOD). DEVELOPMEN THIS CHAPTER CONTINUES WITH T EMBRYONIC DEVELOPMENT, STARTING FROM WHERE THE SEQUENCE LEFT OFF WITH THE DEVELOPMENT OF THE STOMODEUM, FACE, AND NECK IN THE LAST CHAPTER.  MAXILLARY PROCESSES AND GLOBULAR PROCESS (INTERMAXILLARY SEGMENT) WHAT FAIL TO FUSE HAPPENE RESULT D?? > CLEFT LIP – UNILATERAL OR BILATERAL  THREE SOURCES > TWO MAXILLARY PROCESSES PALATAL AND GLOBULAR PROCESS DEVELOPMEN (INTERMAXILLARY SEGMENT) T INWARD GROWTH FROM INNER SURFACES OF EACH (PALATAL SHELF)  INGROWTHS (PALATAL SHELF) LATERAL FROM EACH MAXILLARY PROCESS PALATINE GROWTHS INVAGINATE THE PROCESS ES STOMODEUM  FORMED BETWEEN APPROX. 5 - 12 WEEKS (2 -3 MONTHS) IN UTERO HARD FUSION USUALLY IN AN ANTERIOR PALATE TO POSTERIOR DIRECTION  INGROWTH FROM GLOBULAR PRIMARY PALATE PROCESS (INTERMAXILLARY (PREMAXILL SEGMENT) A) BECOMES ANTERIOR HARD PALATE  TWO LATERAL PALATINE PROCESSES FUSE WITH PREMAXILLA MORE DEVELOPING NASAL SEPTUM FUSES FUSION WITH THESE CLOSES THE ROOF OF MOUTH Figure 5.4A Figure 5.4B Figure 5.4C Figure 5.4D Figure 5.5  FAILURE OF LATERAL PALATINE PROCESSES TO CLEFTS FUSE WITH EACH OTHER OR OF WITH THE PREMAXILLA THE (PRIMARY PALATE) PALATE SLIGHT OR EXTENSIVE > SOFT OR HARD TISSUE APPARENT BY 12 WEEKS Figure 4.9 Figure 5.7 FIGURE 5.6A Figure 5.7 B & C Figure 5.7 D & E Figure 5.8  COMMISSURAL LIP PITS EPITHELIUM-LINED BLIND TRACTS LOCATED AT THE LABIAL COMMISSURE MAY BE SHALLOW OR SEVERAL MILLIMETERS DEEP CONGENITAL LIP PITS MAY ALSO BE OBSERVED NEAR THE MIDLINE OF THE VERMILION BORDER. TREATMENT NONE Fehrenbach, MJ, et al editors. Mosby’s Dental Dictionary, ed 2, Elsevier, 2008 FACIAL AND PALATAL DEVELOPMENT  DEVELOPS FROM 1ST FOUR BRANCHIAL ARCHES I: > MANDIBULAR PROCESS – LATERAL LINGUAL TONGUE SWELLINGS(2), AND TUBERCULUM IMPAR(1) – UNITE TO BECOME THE BODY II, III, IV: COPULA - UNITE TO BECOME THE ROOT/BASE  TWO PARTS BODY (ANTERIOR PART) ROOT/BASE (POSTERIOR PART) DIVIDED BY SULCUS TERMINALIS (V-SHAPED ROW OF TONGUE CIRCUMVALLATE PAPILLAE) FORAMEN CECUM SMALL DEPRESSION LOCATED AT TIP OF V-SHAPE EMBRYONIC ORIGIN OF THYROID GLAND Figure 5.9A Figure 5.9B Figure 5.9 C  CLINICAL CONSIDERATIONS FOR TONGUE DEVELOPMENT ABNORMALITIES OF THE TONGUE ARE UNCOMMON ANKYLOGLOSSIA – SHORT LINGUAL FRENUM EXTENDING TO TONGUE APEX RESTRICTS TONGUE MOVEMENT TO VARYING DEGREES USUALLY STRETCHES WITH TIME & USE IF NOT ADJUSTED OVER TIME – SURGICAL CUTTING OF FRENUM IS CONSIDERED ANKYLOGLOSSIA (TONGUE-TIED) Figure 5.10 QUESTIONS?